Printing cylinders and plates are standardly cleansed manually, by applying a solvent or a detergent that acts on the matter to be eliminated from the cylinders, followed by a mechanical action aiming at removing particles from the cylinders, rinsing with a chemically compatible product and optional drying to prevent formation of a deposit or ring-marks.
Another method uses pressurised air and a gun projecting a material such as sodium bicarbonate or plastic beads for example, so as to remove the matter from the cylinders. Such method generates solid residues that are contaminated by pigmentation and resin, as well as dust, which need be dealt with during the process and disposed of thereafter. Dust may cause damages to surrounding mechanical systems such as ball bearings. The method may be performed on a printing machine or in a workshop, by an operator pointing the gun to the cylinder to be cleansed and linearly displacing K. Safety equipment is necessary for assured respiratory and physical protection the operators. This method is very slow and can mobilize an operator for periods over one hour. Otherwise, an automated gun may be used, moved by a conveyer, and the method is performed within a chamber. The management of dust is thus largely facilitated by the fact that the operation is carried out in a hermetic chamber generally equipped with ventilation system and dust filters. This automated method offers also the advantage of offering very constant results.
In still another method, ultrasonic waves are used to detach the matter from the cylinders in a cleaning bath, typically comprising a warm detergent. This method has been shown to damage the surface of the cylinders if repeatedly used, especially surfaces covered with ceramic. In case of surfaces of steel covered with a fine layer of ceramics, since ceramics and steel have different expansion coefficients, microscopic cracks may be created.
Another method comprises applying a cleaning fluid, such as a detergent, on the surface to be cleansed, and removing it after a delay by rinsing with pressurised water, which allows dislodging particles encrusted within the cells of the surface of the cylinder. However, such method produces large quantity of contaminated water, which must then be treated to neutralize the detergent therein, and the residual waste usually remains contaminated with pigments and other resins. The method may be performed on a printing machine or in a workshop. After the detergent has been applied, an operator points a pressurized water gun to the cylinder to be cleansed and linearly displaces the gun thereover. Vacuum systems may be connected to the gun to monitor spatters and recover contaminated water. The method may also be performed in a chamber, using automated application of detergent and an automated gun. Using a chamber largely facilitates monitoring the spatters and recovering used waters. This automated method offers also the advantage of offering very constant results.